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Lab 2 Quantitative Analysis Of A Sodium Sulfate

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Lab 2 Quantitative Analysis Of A Sodium Sulfate
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Chem 102 - Lab #2
Quantitative Analysis of a Soluble Sulfate

Steven English

Lab Instructor: Dr. Campo
Date: Tuesday, February 5th 2013

Pre-Lab Questions

A. Adding the acid to the sodium sulfate solution results in an increase in the solubility of any free anions present in the sample. This will happen because the present anions will bind with the hydrogen cations present in the acid.

B. The sodium sulfate is boiled because experiments have shown that barium sulfate is 50 times more soluble at 100°C than at room temperature. At the higher temperature, the Ba2+ and the SO42- are more likely to find each other and to form bonds and precipitate more slowly. If this happens too rapidly, then there is a high chance that
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1. Precipitate remains in beaker were washed out with a small amount of distilled water 2. Crystals were added to those already in the funnel and washed 8-10 times with hot water, allowing excess water to drain 3. Silver nitrate was used to test for presence of chloride and washed repeatedly until no ion was present in wash water

E. 1. Sample was set aside for one week

F. 1. A crucible with cover was obtained, and were both cleaned and dried
2. Crucible was marked with blue wax pen to differentiate it from the rest
3. Crucible was then placed on a triangle placed on a ringstand and heated over blue central cone of bunsen burner flame until it glowed red for 10 minutes 4. Was left to cool in desiccator for approximately 20 minutes 5. Weighed on analytical balance 6. Process was repeated to ensure constant mass within ± 0.003 grams was reached

Experimental Procedure (cont.)

G.
1. Filter paper was placed in an uncovered crucible above a small flame on a triangle
2. Crucible was heated gently to dry paper then heat was increased to burn the filter paper off, with the crucible tipped to allow good mixing with oxygen
3. Crucible was covered whenever paper
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When filtering the first sample use two different filter papers were used and ultimately the one with most of the precipitated solid in it had to be stored while there was still a bit of liquid present. This meant that the precipitated material was not able to be rinsed and it is possible that there was some foreign material in the remaining unfiltered supernatant liquid. This foreign material might not have evaporated with the remaining water and could have been left in the filter paper with the precipitated solid, also contributing to the excess mass measured. These two errors, along with possible incomplete burning off of the fliter paper, were probably the source of the majority of the error

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